Glass furnace



July 2s, 1925. 1,547,911

E. T. FERNGREN GLASS FURNACE Filed Feb. 19, 1925 2 sheets-Sheer;

1 l 9 I1Y ATTOR NEY Plantea July ze, 1925.

moon r.

FEBNGBEN, F TOLEDO, OHIO,

ASSIGNOB T O THE LI'BBEY-O'WENS SHEET GLASS COMPANY, OF TOLEDO," OHIO,` A. CORPORATION OF OHIO.

' 4enass run-inca.

A Application led February To a'ZZ 'whom t may comer/n.:-

Be it knownthat I, ENooH T. FERNGREN,

a citizen of Sweden, residingat Toledo, in

the county of Lucas and State of Ohio, have 'invented new and useful Improvements in Glass Furnaces, of which the following is a specification.

This invention' relates to improvements in -the yfurnace construction of sheet lass drawing machines, and more particular y to an improved form of'supporting and heat distributing means for the draw-pot'which contains the molten glass from which the sheet is drawn.

'In a sheet glass drawin apparatus of the type substantially set fori in the patent'to I. W. Colburn, 1,248,809, granted December 4, 1917 ,the molten lass from which the sheet is drawn is carrled in a shallow receptacle or drawot, positioned over a heating chamber whic maintains the glass at the proper drawing. temperature.` Since these pots have a considerable horizontal area, and

therefractory clay o f which they are formed does not have a very high tensilestrength, supports for the central portions of the pot must be providedwithin the heating chamber, these supports usually lbeing in 4 the.

which allow the heating gases to pass therebetween. This structure is substantially disclosed in the atent to Colburn referred 'to above.l This has resulted in an unequal heatingof `the clay within the pot, there bein cooler areas above the contact points of t e supporting stools and hotter, areas therebetween caused by the direct contact of. the heated gases at these points. These silica stools are rather poor conductors of lieat, and the refractory material of which the draw-pot is composed]v is also a rather slow Aconductor so that the different tem erature conditions existingin the bottom o the pot are not materially evened-out or diffused in 'the pot structure, butare assed on tothe molten la thereabove. ince the sheet is drawn om the-pot on 'aline parallel-.to the series of supportmgstools, there will sometimes result alternate hotter or cooler areas 'acro th width of the sheetfcausn'g corded orjstriated' areas in the finished product. object of the avoid this unequal eating of the molten form `-of separate silica stools or. arches present y'invention is tol 1 9, 192s. seriai'naeiass'l.

glasswithin the 'pot-l and the consequent inequalities in the glass sheet. This is accom.

plished by supporting the pot upon a plate or slabof silicon-carbide, or other structurally stable carbide, which has suilicient strength to carry the pot structure when supported adjacent its edges only, the intermediate column of stools or other supports being eliminated, leaving the entire central 'port1oI`1 of the pot exposed to the heated gases inthe furnaceor chamber beneath the pot. This silicon-carbide plate, also has a very high thermal conductivity and helps to diifuse'the heat passing therethrough to the pot in such a way as to eliminate ,the z ones of heat of somewhat varying intensity that may be formed in the furnace by the row of'separate burners whichvpro'ect the heating gases into the furnace cham er.`

The objects and advantages of this invention will be better understood from the following detailed description of two approved forms of furnace construction embodying the principles of this invention.

. In 'the accompanyin drawings:

Fig. 1 isa longitu 'nal vertical section through the draw-pot and'heatig chamber, aken substantially on the' line 1-1 of Fig. Fig. 2 is a transverse vertical section -through the same, takenqsubstantially on the line 2-2 ofFig. 1.

Fig. 3 is a ongitudinal vertical section similar to Fig. 1, through a different modification. This view is taken substantially on the line 3-3 of Fig. 4.-

Fig. 4. is a transverse vertical section taken substantially on the 'line'4-4of Fig. 3.. l

Fig. 5 is a transverse vertical sectiqn through thecarbidesupporting shell, showing how this shell may l built up of a series of separate sections'or lates'.-

Referrin first tojFigs.' land 2, at 1 is shown the elivery end of a continuous tank furnace or other source. of supply for the molten glass 2, which owsdirectly into the open end of the. shal1ow drawpot 0r"`re ceptacle 3. The sheet of. glass 4' is drawn upwardly from the molten glass -2 in the' p gt by an approved-apparatus such as that c ose in the Col urn patent'referred" to above. It will be understodthat the drawmay be used Vwith manyn'other: stems of drawing sheet glass'than the one ere indicated.

The pot 3 is mounted above a furnaceor heating chamber 5, the rear edge 6 of the potbelng carried by the rear wall -7 of this chamber, whereas the front edge 8 is supported by a row of posts or stools 9 rising from the bottom v10 of the furnace chamber.

The drawpot 3, which' is molded from refractory clay or some similar material, has not ysufficient tensile strength to bridge the gap between .the wall 7 and the posts 9 and carry the load of glass '2 contained in the pot. For this reason, an intermediate row of stools or supports,'such as 9, have been used in previous constructions. Ihese intermediate posts not only form cooler areas at their placesA of contact with the bottom of the'pot but also split up the furnace chamber 5'into a series of separate zones orY compartments, and lnterfere with the proper mingling or diifusion of the heated gases withinothe furnace. chamber. In

the present construction, this intermediate '-'row of posts is eliminated and a' slab or plate 11i of a si'licon-carbidematerial is used to span the roof of chamber 5 between the rear wall 7 and the stools or posts 9. The draw-pot 3 rests directly upon this plate or slab 11 of silicon-carbide which material is of high'tenfsile strength and will remain absolutel rigid and carrythe pot and glass centaine therein without sag ng under the heat conditions prevalentin t. e chamber 5.

The siliconscarbide material here used will be abonded granular 'structure of ca rborun-- silicon-carbide ispreferred, where the grains are united in af veryrigid bond by an intergrowth of. interlocking silicon-calrbidecrys` ltals which makes a very rigid and strong material having no bending -point under any tem rature in which 'the material may .exlst wit out breaking down 'The outer surface ofthe plate 1-1 may be coated with silica to reventspalling or flaking of the plate.

e chamber 5 is vheated by a series of sgraced burners A12 which project their iames t ough apertures 13 in the rear wall of the furnace structure. The flamesfrom these burnerspass between the posts 9 across the chamber 5 to the rrear wall 7, are thence deflected upwardly against the'plate 11 forming the roof of the chamber, and thence back beneath this plate, the spent' vand other and of uniforml ratus operates.

' diffuse the heat at the side edgs products of combustion outv through the: assage or flue 15, substantially as indicated y'the arrowsin Figs. 1 and 3.

The removal of 'the center line of stools under the potwill provdea clear open space for the play of these flames from the various burners, and thus. promote a more thorough there will be a more uniform distribution of .the heat units released tothe plate 11 as'the heatinggase's-sweep along the bottom of the pot on theirchamber.

Thel separate Aseveral burners 12 expand 'or' spread out mixing of their fringes of combustion so that l journey. through the furnace'v flames projected from the during their passage through the furnace chamber, andA the outer envelopes Vof the.

adjacent flames where the combustionis the best and the heat the greatest commingle to e5 form. intermediate areas of slightly higher temperature as indicated at 16 in Fi `2 and-4. However, since the'v silicon-car ide plate has a very high thermal conductivity these-'slight varlations linthe heat applied to different areasof the lower face of the late will be distributed or diffused' as the eat passes therethrough to the pot structures so that apractically even and uniformiiow of heat will be imparted to and through -the pot 3 to the molten glass 2. l

Sincethe draw-pots 3 -are often made.

quitel wide, it may-not be practicable in all cases to make a single silicon-carbide plate of suficientarea to underliethe entire lower face of the pot. In such cases, 'the slab or support .may be` built u' of a series of separate plates interlocke together as indicated at 1'( (Fig. 2), the -jointsbeing preferably made secure by fa carborundum cement.

5, a. somewhat different In Figs. 3, 4 and application4 of the principles of this invention is illustrated. In .this case2 the carbide sup'porting' late is embodied 1n the structure ofthe. raw-pot itself. The pot is composed of an' inner glass-containing shell 18 Y of 'refractory clay or similar material and an outer vsupporting shell 19 of'silicom carbide. This outer shell 19 rests upon the rear Wall 7 of the furnace chamberand the supporting stools 9 muchthe same as late 11j, shown in Figs-1 and 2. The'two s elle 18 and 19 are's'e' arately constructed, and'jf the shell 19 will e made somewhat larger than the shell 18 to allowfor the greater expansion of the clay shell wheniheated to the temperatures under which this. appawill function much thesame as the pot 3 and plate 11, already described in connection This double pot structure with Figs. 1 and 2. The side flanges 2 0 on" l the outer shell 19 will: more 'thoroughly than in the previously descr1"d construction.

of the pot j' i The outer shell 19 may be formed in separate sections joined or cemented to-y 2. In a sheet glass drawing apparatus,`

a pot for the molten glass from which the sheet is drawn, incombination with a heating furnace beneath the pot, and a plateof sillcon-carbide of substantially the same dimensions as the pot bottom supporting thepot, the lplate being mounted at its edges on the furnace structure, and its entire central portion being unsup orted and exposed to the heating gases in t e furnace.

3. In a sheet 'glass drawing apparatus, a pot for the molten glass from which the sheetis drawn, comprisingl an inner glassholding shell of refractory clay, and an outer supporting shell of silicon-carbide,

4. In a sheet glass drawing apparatus, a pot for the molten glass from which the sheet is drawn, comprising an inner glass.

holding shell of refractory clay, and an outer supporting shell of silicon-carbide, in combination with a heating furnace beneath the pot, the edges of the outer shell being supported on the furnace structure, while the entire central portion is unsup orted and exposed to the heated gases 1n lthe furnace.

5. In a pot-supporting structurel for 'a sheet glass drawing machine, a siliconcarbide plate of substantially the same dimensions at the pot bottom, and means for supporting the plate adjacent its edges only.

, 6. In a sheet-glass drawing furnace con-l clay struction, a draw-pot of a refractor composition containing the molten g ass, a silicon-carbide plate extending under said pot to support the same, and suitable reractory members on which the slab rests -along its border portions, the central portionsl of the plate being unsupported.

7 In a sheet-glassv drawing apparatus, a

pot structure from which a sheet of lassA may be drawn, in combination with a eating furnace and a slab of refractory material supported from the furnace structure for supporting the border portionsof said pot above the heating space of said furnace,

said heating space being open and unobstructed beneath said slab to promote the free movementof heating media therethrough.

. 8. In the art of drawing sheet glass, the method yot transmitting heat to the glass which is under tractive stress in the drawpot, which consists in transmitting the4 heat which is produced bya series of overlapping zones of combustion through the walls ofthe draw-pot and the glass therein by an intermediate material of silicon-carbide for 4 the purpose of locally equalizing the variable ratios in velocity 'and volume of heat penetration. I v

9. The method of transmitting heat to a body of glass from which a sheetis being drawn, which consistsin applying the heat which is being supplied to said body from a heating space t-herebeneath, first, to a material having a high 4rate of conductivity,

thence to a material of relatively slow conductiv-ity, and thence to the lass for the purpose of promoting equal distribution ofy heat to the substratums in the body of glass under drawing stress'.

10. The method of equalizing the iiow of heat units into the substratums of a body of glass in a draw-pot from which' a sheet is being drawn, which consists in forming an approximately uniform column of heat in a heating chamber beneath the pot, by transfusing the borders of a series4 of separate zones of combustion and by passm said heat through a uniformly graded an spaced material of high thermal conductivity in` its transit toward the pot. 11. A pot for use in sheet .glass apparatus,

comprising an inner refractory material v uniformi to the inner member and 'glass containe therein.

Si ed. at Toledo, in the county of Lucas,

and tate of Ohio, this 17th day of February, 1923.

ENOCH T. FERNGREN. 

